Encapsulation method and leadframe for leadless semiconductor packages

ABSTRACT

The present invention relates to an encapsulation method of leadless semiconductor package. The method comprises the steps of: (a) attaching a plurality of dice to the die pads on the cavities of a leadframe, the leadframe having a plurality of cavities arranged in matrix configuration and classified into a plurality of columns and a plurality of rows; (b) electrically connecting the die on the die pad to a plurality of conducting portions of the leadframe; and (c) longitudinally injecting the mould compound into the cavities of the column via a plurality of longitudinal gates of the leadframe to package the dice on the cavities of the column, the longitudinal gates mounted between the cavities of the column. The method of the invention does not need a film to prevent the molding flash, and can solve the problem of remaining the molding flash on the conducting portion. The method of the invention does not use the expensive cutting equipment so as to decrease the cost and to upgrade the efficiency.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an encapsulation method and leadframe of semiconductor package, more particularly, to an encapsulation method and leadframe of leadless semiconductor package.

[0003] 2. Description of the Related Art

[0004] The conventional encapsulation method for packaging semiconductor is classified into two kinds. The first encapsulation method is applied to semiconductor package with lead, as shown in FIG. 1. A die is mounted on a cavity 11 of a leadframe 1, and is connected to the pin of the leadframe 1. The leadframe 1 has runner 12, and the runner 12 is connected to the cavity 11 by sub-runner 13 and gate 14. The gate 14 is a injection inlet between the sub-runner 13 and the cavity 11. Therefore, the mould compound is injected into the runner 12 via the sub-runner 13, the gate 14 to the cavity 11 so as to package the die in the cavity 11. This encapsulation method must have the space of the runner 12 and the sub-runner 13 so as to decrease the number of die within the area, and cannot have high packaging efficiency.

[0005] The second encapsulation method is applied to leadless semiconductor package, as shown in FIG. 2. A plurality of dice are placed on a cavity 21. The mould compound is injected into the cavity 21 to package the dice. Therefore, the number of die within the leadframe is increased, and the cost of the leadframe can be decreased. However, the second method must use a cutting equipment to cut the packaged semiconductor devices into individual pieces, and the cutting equipment is usually expensive. Therefore, the cost of the second method is high. Furthermore, after the semiconductor devices are cut, every piece of the semiconductor device must be picked to a tray or a tube so that the step of the second method is complex and the efficiency of the second method is low.

[0006] Besides, as shown in FIG. 3, the packaged semiconductor device 3 has no pins, but a plurality of conducting portions 31 for connecting to a circuit board. When the leadless semiconductor is packaged, the molding flash must not remain on the conducting portion 31. Therefore, during the packaging process, a film at the bottom of the semiconductor is needed to prevent the molding flash from remaining on the conducting portions. Such a film will increase the cost of the second method and degrade the efficiency.

[0007] On the other hand, the second method must utilize an upper mold and a lower mold to clamp the periphery of the leadframe 2, and the mould compound is injected into the cavity 21 formed by the upper and lower molds. Because the cavity 21 is large, the upper and lower molds can only clamp the periphery of the leadframe 2. The middle portion of the cavity 21 cannot be clamped by the upper and lower molds. Therefore, that will easily cause that the molding flash remains on the conducting portion 31.

[0008] Therefore, it is desirable to provide a creative and improved encapsulation method and leadframe to overcome the above problem.

SUMMARY OF THE INVENTION

[0009] One objective of the present invention is to provide a leadframe of leadless semiconductor package. The leadframe comprises: a plurality of cavities and a plurality of longitudinal gates. Each cavity has at least one die pad for supporting at least one die. Each cavity has a plurality of conducting portions for electrically connecting the die on the die pad. The cavities are arranged in matrix configuration and classified into a plurality of columns and a plurality of rows. The longitudinal gates are mounted between the cavities of the column. The mould compound is injected in the cavities of the column via the longitudinal gates to package the dice on the cavities.

[0010] Therefore, the leadframe of the invention does not have the runner of the conventional leadframe, and can have more space to support more dice. The density of die on the leadframe can be high, and the packaging efficiency can be improved. Besides, the mould compound on the runner can be minimized by using the leadframe of the invention so as to decrease the manufacturing cost.

[0011] Another objective of the invention is to provide an encapsulation method of leadless semiconductor package. The method comprises the steps of: (a) attaching a plurality of dice to the die pads on the cavities of a leadframe, the leadframe having a plurality of cavities arranged in matrix configuration and classified into a plurality of columns and a plurality of rows; (b) electrically connecting the die on the die pad to a plurality of conducting portions of the leadframe; (c) longitudinally injecting the mould compound into the cavities of the column via a plurality of longitudinal gates of the leadframe to package the die on the cavities of the column, the longitudinal gates mounted between the cavities of the column.

[0012] The method of the invention does not need a film to prevent the molding flash, and can solve the problem of remaining the molding flash on the conducting portion. The method of the invention does not use the expensive cutting equipment so as to decrease the cost and to upgrade the efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 shows a conventional leadframe for packaging semiconductor with lead.

[0014]FIG. 2 shows a conventional leadframe for packaging leadless semiconductor.

[0015]FIG. 3 shows a conventional leadless semiconductor device.

[0016]FIG. 4 shows a top-view of leadframe of leadless semiconductor package according to the present invention.

[0017]FIG. 5 shows a flow chart illustrating an encapsulation method of leadless semiconductor package according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0018] Referring to FIG. 4, according to the invention, a leadframe 4 of leadless semiconductor package comprises a plurality of cavities 41, 42, 43, 44, 45, 51, 52, 53, 54, 55 and a plurality of longitudinal gates 46, 47, 48, 49, 56, 57, 58, 59. Each cavity has a die pad (not shown in the figure) for supporting a die. The die 411 is attached to the die pad on the cavity 41. Each cavity has a plurality of conducting portions for electrically connecting to the die on the die pad. For example, the cavity 41 has three conducting portions 412, 413 and 414. In the embodiment of the invention, each cavity has a die pad for supporting a die. To improve the efficiency, each cavity can have a plurality of die pads for supporting a plurality of dice.

[0019] The cavities are arranged in matrix configuration, and are classified into a plurality of columns and a plurality of rows. For example, the cavities 41, 42, 43, 44 and 45 form a first column, and the cavities 51, 52, 53, 54 and 55 form a second column. The cavities along the direction of cavities 41 and 51 form a first row, and the cavities along the direction of cavities 42 and 52 form a second row.

[0020] The longitudinal gates 46, 47, 48, 49, 56, 57, 58 and 59 are mounted between the cavities of the column. For example, the longitudinal gate 46 is mounted between the cavity 41 and the cavity 42 for connecting the cavity 41 and the cavity 42. Similarly, the longitudinal gate 47 is mounted between the cavity 42 and the cavity 43 for connecting the cavity 42 and the cavity 43. Therefore, the cavities 41, 42, 43, 44 and 45 are connected by the longitudinal gates 46, 47, 48 and 49. Similarly, the cavities 51, 52, 53, 54 and 55 are connected by the longitudinal gates 56, 57, 58 and 59.

[0021] The mould compound is injected into the cavities of the column of the leadframe 4 via the longitudinal gate to package the die in the cavity. For example, firstly the mould compound is injected into a first longitudinal gate 40 on the first column, and then flows into the cavity 41 of the first column via the first longitudinal gate 40. In sequence, the mould compound flows into the longitudinal gate 46, the cavity 42, the longitudinal gate 47, the cavity 43, the longitudinal gate 48, the cavity 44, the longitudinal gate 49, the cavity 45 to package the dice in the cavities of the first column.

[0022] The leadframe 4 of the invention does not have the runner 12 as shown in the conventional leadframe 1, and the leadframe 4 can have more space to support more dice. The density of die on the leadframe 4 can be high, and the packaging efficiency can be improved. Besides, the mould compound on the runner can be minimized by using the leadframe 4 of the invention so as to decrease the manufacturing cost.

[0023] According to the embodiment of the invention, to further improve the packaging quality, the leadframe 4 further comprises a plurality of horizontal gates 61, 62, 63, 64 and 65. The horizontal gates are mounted between the cavities of the row. For example, the horizontal gate 61 is mounted between the cavity 41 and the cavity 51 for connecting the cavity 41 and the cavity 51. Similarly, the horizontal gate 62 is mounted between the cavity 42 and the cavity 52 for connecting the cavity 42 and the cavity 52. When the mould compound is injected into the cavity of the column, the mould compound can flow into the horizontal gates so as to balance the pressure between the cavities of the row. The bubbles induced in the cavities of the mould compound can be drained by the horizontal gates to further improve the packaging quality.

[0024] Referring to FIG. 5, the flow chart illustrates an encapsulation method of semiconductor package according to the present invention. In step 501, the dice are attached to the die pads in the cavities of the leadframe 4. The leadfreame 4 has a plurality of cavities arranged in matrix configuration and classified into a plurality of columns and rows. In step 502, the die is electrically connected to the conducting portion of the leadframe 4.

[0025] In step 503, the mould compound is injected longitudinal to package the die. The mould compound is injected into the cavities of the column via the longitudinal gates to package the dice on the cavities of the column. The longitudinal gates are mounted between the cavities of the column.

[0026] In step 503, the mould compound can flow into the horizontal gates so as to balance the pressure between the cavities of the row and to drain the bubbles induced in the cavities of the mould compound. The horizontal gates are mounted between the cavities of the row.

[0027] The method of the invention does not need a film to prevent the molding flash, and can solve the problem of remaining the molding flash on the conducting portion. The method of the invention does not use the expensive cut equipment so as to decrease the cost and to upgrade the efficiency.

[0028] While embodiments of the present invention have been illustrated and described, various modifications and improvements can be made by those skilled in the art. The embodiments of the present invention are therefore described in an illustrative but not restrictive sense. It is intended that the present invention is not limited to the particular forms as illustrated, and that all the modifications not departing from the spirit and scope of the present invention are within the scope as defined in the appended claims. 

We claim:
 1. A leadframe of leadless semiconductor package, comprising: a plurality of cavities, each cavity having at least one die pad for supporting at least one die and a plurality of conducting portions for electrically connecting the die on the die pad, the cavities arranged in matrix configuration and classified into a plurality of columns and a plurality of rows; and a plurality of longitudinal gates mounted between the cavities of the column, the mould compound injected in the longitudinal gates to package the dice on the cavities.
 2. An encapsulation method of leadless semiconductor package, comprising the steps of: (a) attaching a plurality of dice to die pads on cavities of a leadframe, the leadframe having a plurality of cavities arranged in matrix configuration and classified into a plurality of columns and a plurality of rows; (b) electrically connecting the die on the die pad to a plurality of conducting portions of the leadframe; and (c) longitudinally injecting the mould compound into the cavities of the column via a plurality of longitudinal gates of the leadframe to package the dice on the cavities of the column, the longitudinal gates mounted between the cavities of the column. 